Benzofurancarboxamides and therapeutic agents

ABSTRACT

A benzofurancarboxamide of the formula: ##STR1## where: X is hydrogen or methoxy, 
     R 1  is a radical of the formula: ##STR2##  wherein R 3  to R 5  are each, independently of one another, hydrogen or C 1-6  alkyl, R 6  is a branched or unbranched C 1-6  alkyl, or benzyl which may be methyl- or halogen-substituted on the nucleus, and   is a single or double bond.

This is a division of application Ser. No. 07/598,785, filed on Oct. 15, 1990, now U.S. Pat. No. 5,151,437; which is a continuation of Ser. No. 07/221,653 filed Jul. 20, 1988, now abandoned.

The present invention relates to novel benzofurancarboxamides having basic substituents, to a process for the preparation thereof, and to therapeutic agents containing them, especially for the therapy of a number of disorders of the central nervous system, exogenous psychological disturbances and dyskinesias.

2-Methoxy-substituted benzamides having a basic side-chain are described in the Literature as drugs having an antidopaminergic action (Bernd Testa, J. Med. Chem. 26 (1983), 203-207). The best-known compound is sulpiride, but the oral availability of this is unsatisfactory.

We have found that compounds of the general formula I are distinctly superior to sulpiride in their central antidopaminergic action. This high central availability is surprising in view of the aromatic substitution pattern typical of compounds having a peripheral action (B. Pourrias, Arch. int. Pharmacodyn. 274, (1985) 223).

In the general formula I ##STR3## X is hydrogen or methoxy, R¹ is a radical of the formula

    --CHR.sup.2 --CHR.sup.3 --(CR.sup.4 R.sup.5).sub.n --NR.sup.6 R.sup.7II

where R² to R⁵ are each, independently of one another, hydrogen or alkyl of 1 to 6 carbon atoms, R⁶ and R⁷ are, independently of one another, alkyl of 1 to 6 carbon atoms, which may be branched, or benzyl which may be methyl- or halogen-substituted on the nucleus, and, in each case, one or two of R² to R⁶ can form together with R⁷ an alkylene chain of 2 to 6 carbon atoms which can be interrupted by an ether oxygen; n is 0 or 1.

The double bond in the furan ring can be hydrogenated.

Thus, the following possible general structures for the group --HN--R¹ emerge from the general formula II: ##STR4##

Examples are: ##STR5##

The compounds of the general formula I are prepared by reacting a reactive acid derivative III with an amine H₂ N--R¹ by generally known methods. ##STR6##

Y is a leaving group which can be displaced by nucleophiles, for example a chlorine or bromine atom, a methoxy or ethoxy group, or an oxysuccinimide, 1-imidazolyl or ethoxycarbonyloxy radical. The preparation of these acid derivatives from the acid IV, as well as the reaction thereof with amines, is known from the literature and is described, for example, in Houben-Weyl, Methoden der Org. Chemie (Methods of Organic Chemistry), 4th edition, E5, pages 941-991.

The acid IV is prepared in a simple manner by oxidative ring opening of the natural furochromones khellin Va and visnagin Vb (JACS 75, (1953) 4992). ##STR7##

This means that the compounds of the general formula I can be obtained distinctly more easily than other antidopaminergic benzamides in which suitable substituents have to be introduced into the benzene ring by synthesis (J. Med. Chem. 21, (1986) 61, 25, (1982) 1280).

Compounds of the general formula I in which the furan ring is hydrogenated can be obtained in a similar manner starting from the acid ##STR8## The latter can be prepared, for example, by hydrogenation of the acid IV or of one of its salts by conventional methods.

Some of the compounds I according to the invention have a center of chirality and are obtained as racemates which can be separated into the enantiomers by conventional methods, for example by formation of diastereomeric salts with optically active acids. It is also possible to obtain the optically pure compounds I by use of the enantiomerically pure amine H₂ N--R¹.

The compounds according to the invention are suitable for the therapy of a number of disorders of the central nervous system, especially for the treatment of psychotic diseases such as schizophrenia, as well as for the treatment of exogenous psychological disturbances, especially those associated with a diminution of drive. The substances can also be used for the treatment of dyskinesias (e.g. Huntington's chorea and tardive dyskinesias after neuroleptic therapy).

Further areas of use are the therapy of vomiting, of gastric ulcer or duodenal ulcer and of disturbances of motility of the gastrointestinal tract.

The therapeutic agents or compositions are prepared with the customary liquid or solid carriers or diluents and the auxiliaries customarily used in pharmaceutical technology, appropriate for the desired mode of administration and having a dosage suitable for use, in a conventional manner, for example by mixing the active compound with the solid and liquid carriers and auxiliaries customary in such products.

The agents can be administered orally, parenterally or topically. Examples of such compositions are tablets, film-coated tablets, sugar-coated tablets, capsules, pills, powders, solutions or suspensions, or solutions for infusion or injection.

The therapeutic agents can contain the compounds to be used according to the invention in a single dose of 0.03 to 3 mg per kg weight, i.e. 2 to 200 mg per tablet, and can be administered in one or more doses each day, depending on the nature and severity of the diseases.

Examples of auxiliaries customarily used in pharmaceutical technology are, for local use, alcohols such as ethanol and isopropanol, ethoxylated castor oil or ethoxylated hydrogenated castor oil, polyacrylic acid, glycerol monostearate, liquid paraffin, petrolatum, lanolin, polyethylene glycol, polyethylene glycol stearate and ethoxylated fatty alcohol, and for systemic use lactose, propylene glycol and ethanol, starch, talc and polyvinylpyrollidone. It is possible to add to the products an anti-oxidant, for example tocopherol and butylated hydroxyanisole or butylated hydroxytoluene, or additives to improve the flavor, stabilizers, emulsifiers, bleaching agents etc. The prerequisite is that all the substances used in the preparation of pharmaceutical compositions are toxicologically acceptable and compatible with the active compounds used.

Preparation of 2,3-dihydro-6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid (as precursor).

5 g of 6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid in 75 ml of ethanol/25 ml of H₂ O/0.8 g of NaOH are hydrogenated in the presence of 1 g of Pd/C (10%) under atmospheric pressure and at 50° C. until uptake of hydrogen is complete. The mixture is filtered, the ethanol is removed by distillation, the aqueous phase is acidified, and the solid is filtered off with suction. 3.7 g of product are obtained and reacted further without purification.

N-hydroxysuccinimide ester of 6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid (as precursor)

A solution of 21.0 g of dicyclohexylcarbodiimide in CH₂ Cl₂ is added dropwise at room temperature to 24.3 g of 6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid and 11.7 g of N-hydroxysuccinimide in 300 ml of CH₂ Cl₂. The mixture is stirred at room temperature for 3 h, and is filtered, the filtrate is washed with water, and the solvent is removed in vacuo. Recrystallization of the residue from isopropanol provides 20.7 g of product, melting point 136° C.

The following precursors are prepared, for example, in a similar manner:

N-hydroxysuccinimide ester of 6-hydroxy-4-methoxybenzofuran-5-carboxylic acid, melting point 134° C.

N-hydroxysuccinimide ester of 2,3-dihydro-6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid, melting point 133° C.

EXAMPLE 1 N-[(1-Ethyl-2-pyrrolidinyl)methyl]-6-hydroxy-4,7-dimethoxybenzofuran-5-carboxamide

4.7 g of 1-ethyl-2-aminomethylpyrrolidine were added dropwise to a cooled solution of 10 g of the N-hydroxysuccinimide ester of 6-hydroxy-4,7-dimethoxybenzofuran-5-carboxylic acid in 100 ml of CH₂ Cl₂. The mixture was stirred at room temperture overnight and then washed with NaHCO₃ solution and water. the organic phase was separated off and dried with Na₂ SO₄, and the solvent was removed by distillation. The residue was recrystallized from ethanol. 7.0 g were obtained, melting point 86° C. The following compounds according to the invention were prepared in a similar manner starting from the appropriate acid and amine components.

    __________________________________________________________________________     Example No.                                                                           HNR.sup.1             Melting point [°C.]                        __________________________________________________________________________      ##STR9##                                                                       2                                                                                     ##STR10##            212 (Hydrochloride)                                3                                                                                     ##STR11##            198 (Hydrochloride)                                4                                                                                     ##STR12##            138                                                5                                                                                     ##STR13##            128                                                6                                                                                     ##STR14##            Oil                                                7                                                                                     ##STR15##            121                                                8                                                                                     ##STR16##            151                                                9                                                                                     ##STR17##            Oil                                               10                                                                                     ##STR18##            217 (Hydrochloride)                               11                                                                                     ##STR19##            172 (Hydrochloride)                               12                                                                                     ##STR20##            205 (Hydrochloride)                                ##STR21##                                                                     13                                                                                     ##STR22##            189 (Hydrochloride)                               14                                                                                     ##STR23##            204 (Hydrochloride)                               15                                                                                     ##STR24##            82                                                16                                                                                     ##STR25##            127                                               17                                                                                     ##STR26##            249 (Hydrochloride)                                ##STR27##                                                                     18                                                                                     ##STR28##            153 (Hydrochloride)                               19                                                                                     ##STR29##            151 (Hydrochloride)                               __________________________________________________________________________ 

We claim:
 1. A benzofurancarboxamide of the formula: ##STR30## where: X is hydrogen or methoxy,R¹ is a radical of the formula: ##STR31## wherein R³ to R⁵ are each, independently of one another, hydrogen or C₁₋₆ alkyl, R⁶ is a branched or unbranched C₁₋₆ alkyl, or benzyl which may be methyl- or halogen-substituted on the nucleus, and is a single or double bond.
 2. The benzofurancarboxamide of claim 1, wherein X is methoxy, R¹ is substituted pyrrolidinyl and R³ to R⁵, are each hydrogen, R⁶ is benzyl and is a double bond.
 3. The benzofurancarboxamide of claim 1, where X is methoxy, R¹ is substituted pyrrolidinyl and R³ to R⁵ are each hydrogen, R⁶ is benzyl and is a single bond.
 4. The benzofurancarboxamide of claim 1, wherein X is methoxy, R¹ is substituted pyrrolidinylmethyl and R³ to R⁵ are each hydrogen, R⁶ is ethyl and is a double bond.
 5. The benzofurancarboxamide of claim 1, wherein X is methoxy, R¹ is substituted pyrrolidinylmethyl and R³ to R⁵ are each hydrogen, R⁶ is ethyl and is a single bond.
 6. The benzofurancarboxamide of claim 1, wherein X is hydrogen, R¹ is substituted pyrrolidinylmethyl and R³ to R⁵ are each hydrogen, R⁶ is ethyl and is a double bond.
 7. A therapeutic agent, which comprises: from 2 to 200 mg of the benzofurancarboxamide of claim 1 as the active compound in combination with a pharmaceutically acceptable carrier. 